Method for continuously generating bevel gears with straight teeth



Feb. 13, 1962 G. APlTZ 3,020,808

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METHOD FoR CONT OUSLY GENERATING BEVEL GEARS WI STRAIGHT TEETH Filed Sept. 23, 1958 19 Sheets-Sheet '7 CuH/hq arcs l I i l n F ig 7mvs-raP Feb. 13, 1962 APlTz 3,020,808

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METHOD FOR CONTINUOU SLY GENERATING BEVEL GEARS WITH STRAIGHT TEETH Filed Sept. 23, 1958 19 Sheets$heet 12 CuH-er head Fig. 72 %w $92M Feb. 13, 1962 rrz 3 20,808

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METHOD FOR CONTINUOUSLY GENERATING BEVEL GEARS WITH STRAIGHT TEETH Filed Sept. 25, 1958 19 Sheets-Sheet 15 Roll body for gene/175019 grealer wheel Doll ody c-e n 1'':

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METHOD FOR CONTINUOUSLY GENERATING BEVEL GEARS WITH STRAIGHT TEETH Filed Sept' 1958 19 Sheets-Sheet 16 0 L -ll 5 I L .T Rollbooly for qenerexlhgg greater bevel gear .2 B It l Lesser beve wheel Cutter head for qrealer bevel wheel Plane of crown wheel Cutter head for lesser bevel wheel i Rot! body for qenerazlhg a q, lesser bevel gear oak 0 x w om 8 3 0,

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3,020,803 METHGD FGR CGNTINUOUSLY GENERATING BEVEL GEARE WKTH STRAIGHT TEETH Gerhard Apitz, Hamburg, Germany, assignor to Heidenreich dz I-Iarheck, Hamburg, Germany, a German partnership Filed Sept. 23, 1958, Ser. No. 762,888 Claims priority, application Germany (Pct. 1, 1957 16 Claims. (Cl. 9tl-5) KNOWN METHODS Bevel gears with straight teeth are today manufactured generally in rolling processes using planing or milling, in copying methods by planing or in breaching methods.

The planing in the copying methods necessitates the highest working time for the tooth formation and comes into consideration only for the largest wheels (over 750 mm. diameter) with large modulus. In the planing in the rolling indexing method, two rams or sliding heads of the roller members, which support the planing tool, are so arranged that on the forward and backward movement of the rams, the planing tool works toward the apex of the cone, whereby the tooth is formed. The wheel is secured on the indexing head. The forward and backward movement of the planer tool acts on the whole material of the wheel blank and cuts out a gap between the teeth. After the total tooth depth is reached, an additional rotating movement is imparted to the entire roller member and the indexing head besides the forward and backward movement of the planer tool, so that the tooth profile can be rolled or generated. After the tooth profile has been rolled the whole roll body is withdrawn so that the planer tool comes free from the wheel blank. Now the roller member turns back to its original position and the indexing head travels likewise through a return movement and at the same time through an indexing movement whereby the next tooth gap can be cut. Thus in the manufacture of a bevel gear it must be rolled and indexed as often as the wheel possesses teeth. This repeated rolling and indexing naturally mean a considerable expenditure of time.

The process for roller milling is similar to the roller planing process except that the planing tool is replaced by a milling tool. The cutter does not undergo a forward and backward movement but only a rotational movement about its axis. In this way the tooth base is not straight as in planing but concave. It must always be cut lower so that the necessary active profile reaches over the whole breadth of the tooth. The cutter next cuts out also a tooth space which is then rolled. After the rolling the milling cutter is Withdrawn from the wheel blank and there follows now a hack rotation into the original position and the indexing after which the next tooth space can be worked on.

The cutting goes indeed more quickly than the planing, it however likewise requires rolling and indexing as often as the wheel has teeth. This kind of cutting is also known as rolling cutting.

In the breaching process, a rounded breach is used which works in a way similar to the cutter. The broach knives are arranged on a round base similar to the milling cutter teeth. The pre-cutting knives are different. in their height, so that they first part the teeth spaces. The then following finishing knives finally cut the profile on both sides of a space. Here no rolling takes place. Because the tooth profile varies along the breadth of the tooth each finishing cutter makes only a wholly determined cut. Each successive finishing cutter possesses a diiferent profile. So that each finishing cutter can cut a profile appropriate to itself in the wheel blank the broaching tool must move along the breadth of the tooth in broaching. The broach teeth are difficult to manufacture because the cutting sides of these cutters must correspond precisely to the profile to be out which as mentioned varies from cutter to cutter. The breaching tools are thus high in price.

The broaching is very quick. On each reciprocation of the broaching tool a tooth space is finished. There is in this case no rolling but only indexing. There is therefore indexing as often as the wheel has teeth.

The cutting edges of the planer tool and the milling cutters are linear. With these linear cutting edges, the tooth profile is rolled from tooth to tooth in the indexing process. The cutting edges of the broaches have a profiled form. The tooth spaces are cut. out in the indexing process without rolling.

TECHNICAL PROBLEM As appears from the state of the art all accurate bevel gears are today manufactured in roller indexing processes or bro-aching processes. Because the rollingand indexing from tooth to tooth is time consuming, a continuous processfrom which the individual rolling and indexing steps are omitted can bring considerable advantages in respect of working time.

The technical problems then consist in finding a continuously working process for bevel gears with linear teeth from which the separate rolling and indexing steps are omitted.

The attached drawings will help to interpret the invention more clearly, said drawings explaining the process of the invention.

FIG. 1 shows the generation of a straight-lined hypocycloid when a circle K goes through a stationary circle K the diameters of the circles being at a ratio of 1:2.

FIG. 2 shows the generation of a straight-lined hypocycloid when the circle K is rotating about its middle point M and the circle K is rotating about its middle point M with both the circles rotating at the same speed.

FIG. 3 is a schematic view showing that the lines extending vertically of the hypocycloid which are erected at the respective points of intersection are always intersecting in the point P.

FIG. 4 is a schematic view showing that the individual points of the straight-line may also be generated by several cutters disposed in displaced arrangement, so that there is no necessity to keep to the ratio of the diameters of 1:2.

FIG. 5 is a schematic view of the flank line out in accordance with FIG. 4.

FIG. 6 shows the principle of the cutting process.

FIG. 7 shows the position of the cutting arcs.

FIG. 8 shows the configuration of the cutting arcs generated.

FIG. 9 shows the configuration of the cutting arcs generated.

FIG. 10 is a schematic view of the position of the cutters with the same direction of rotation of cutter heads having two cutter series.

FIG. 11 is a schematic view of the position of the cutters with opposed direction of the cutter heads having two cutter series.

FIG. 12 is a schematic view of the position of the cut- 

